According to the US Centers for Disease Control and Prevention (CDC), in the year 2007, 35% of US high school students were currently sexually active and 47.8% of US high school students reported having had sexual intercourse.[1] This percentage has decreased slightly since 1991.[2] According to a 1994 study, every year an estimated one in four sexually active teens contracts a sexually transmitted infection (STI).[3]Teenage pregnancy is four times as prevalent in the United States as in the European Union.[4] However, US teen pregnancy rates have been steadily declining for decades, according to the Centers for Disease Control and were at a "record low" as of 2012.[5]

In 1999, a Kaiser Family Foundation study found that 95% of public secondary schools offered sex education programs. More than half of the schools in the study followed a comprehensive approach that included information about both abstinence and contraception, while approximately one third of schools provided students with abstinence-only sex education.[6] In 2002, most Americans favored the comprehensive approach.[6] A 2000 study found that almost all schools included information about HIV, the virus that causes AIDS, in their curricula.[6] There have been efforts among social conservatives in the US government to limit sex education in public schools to abstinence-only sex education curricula.[6] The effectiveness of abstinence-only programs has been an issue of controversy.[7][8]

This section is missing information about contraceptive/protection use among homosexual teens. Please expand the section to include this information. Further details may exist on the talk page.(November 2013)

Some studies have indicated that approximately half of sexually active teens have had sexual partners whom they were not dating.[9] This has led to belief in a "hookup culture" in which casual sex is more tolerated among teens and young adults. However, other research indicates that hookup culture is largely a social myth and evidence for greater casual sex among the young is lacking.[10] It may be that news coverage of hookup culture creates a false belief among the young that such activity is occurring even if they themselves are not participating.[11]

Self-report surveys suggest that half of all 15- to 19-year-olds have had oral sex. That percentage rises to 70% by the time they turn 19, and equal numbers of boys and girls participate.[12] Research indicating that oral sex is less risky to teens' emotional and physical well being than vaginal sex has been advanced;[13] researchers at the University of California do not believe this conclusion is warranted.[14] They found that oral sex, as well as vaginal sex, was associated with negative consequences.[14] Of adolescents engaging in oral sex only, girls were twice as likely as boys to report feeling bad about themselves and nearly three times as likely to feel used.[15] Despite their behaviors, 90% of adolescents "agree that most young people have sex before they are really ready."[16]

The average age of first sexual intercourse in the United States is 17.0 for males and 17.3 for females,[17][18] and this has been rising in recent years.[19] The percentage of teens who are waiting longer to have sex has been increasing.[19] For those teens who have had sex, 70% of girls and 56% of boys said that their first sexual experience was with a steady partner, while 16% of girls and 28% of boys report losing their virginity to someone they had just met or who was just a friend.[19]

Teens are using birth control (contraceptives) more today when they lose their virginity than they did in the past, and this is in part due to the AIDS epidemic.[19] Of sexually experienced adolescents, 78% of girls and 85% of males used at least one contraceptive when they lost their virginity.[19] A detailed qualitative study of girls' loss of virginity found that their experiences "were almost all quite negative (and, in some cases, horrific)."[20] Before age 15, "a majority of first intercourse experiences among females are reported to be non-voluntary."[21]

Adolescents who are better students initiate sexual activity later than those who are poor students. In addition, among those seventh and eighth graders, those with personal and perceived peer norms that encourage adolescents to refrain from sex are less likely to engage in it.[22]

The percentage of teenagers who report they are currently sexually active has been dropping since 1991.[23] By 2005, the overall percentage of teenagers reporting that they were currently sexually active was down to 33.9%.[1] A lower number of sexually active teens is "quite positive in terms of their health and their well-being."[24]

The condom is the most popular form of contraception used by teenagers.[25] Based on statistics collected from 2006-2008, 79% of females and 87% of males used some form of contraception the first time they had sex.[25] Among sexually active 15- to 19-year-olds, from 2002 to 2010 more than 80% of females and more than 90% of males reported using at least one method of birth control during their last intercourse.[19][26] In 1995, only 71% of girls and 82% of boys reported using contraception the last time they had sex.[19] In 2006–2010, one in five sexually active female teens (20%) and one-third of sexually active male teens (34%) reported having used both the condom and a hormonal method the last time they had sex.[19] Less than 20% of girls at risk for unintended pregnancy were not using any contraceptive method the last time they had sex.[19] Calendar abstinence, or the rhythm method, was used by 17% of female teens in 2006-2008.[25]

Sexual abstinence is the practice of refraining from some or all aspects of sexual activity for medical, psychological, legal, social, financial, philosophical, moral or religious reasons. For the last twenty years, abstinence rates among American adolescents have risen. The percentage of high school students in the US who reported that they have ever had sexual intercourse dropped from 54.1% in 1991 to 47.8% in 2007[1] and to 43% in 2011.[27] A cross-sectional survey in 1998 found that fear of pregnancy was the most commonly cited reason for choosing abstinence, especially among girls, as well as boys who had caused a pregnancy in the past. Other reasons included a fear of sexually transmitted infections, a lack of desire, being afraid of getting caught, and the belief that sex was not appropriate for someone of their age.[28]

Epidemiologists at the Center for Disease Control emphasize that for sex education to be effective, it should take place before teens become sexually active.[29]

Both adolescents who have never had sex and those who have chosen to become abstinent after engaging in sexual behaviors cite the negative consequences of sex as reasons why they choose not to have sex.[28] Girls of all ages and experience levels were more likely than boys to cite the fear of pregnancy and sexually transmitted diseases.[28] Virgin boys were more likely than girls to say they believed most students did not have sex.[28]

Boys who caused a pregnancy in the past were more than twice as likely to become abstinent after this episode than boys who had not. However, for girls, a past pregnancy had little correlation with secondary abstinence.[28] Fear of pregnancy, wanting to wait until marriage, and not wanting to have sex were cited more often by virgins in the 12th grade than they were by 9th graders.[28] Of the sexually experienced who are now practicing abstinence, girls were more likely than boys to say a lack of desire, fear of STDs, being afraid of getting caught, the belief that sex was not appropriate for someone their age, and that their parents had taught them the advantages of waiting as reasons why they made their decision.[28]

Among young people engaging in some form of sexual activity, definitions of virginity differ. Virginity is usually defined as the state of a person who has never engaged in sexual intercourse, although there are some gray areas. For example, teenagers that engage in oral sex but not penile-vaginal sex may still identify themselves as virgins; this is sometimes termed technical virginity. Of those polled, 70% of adolescents aged 12–16 believed oral sex did not disqualify someone from virginity and 30% believed they were still abstinent.[31][32]

Of adolescents age 12–16, 83% believe a person is still a virgin after engaging in genital touching, and 70% said they believed one retained their virginity after having oral sex. Additionally, 16% considered themselves virgins after anal sex. However, 44% believed that one was abstinent after genital touching and 33% believed one could have oral sex and still remain abstinent. Of anal and vaginal sex, 14% believed you could engage in the former and 12% said you could participate in the latter while still remaining abstinent.

Identifying oneself as a virgin even after limited sexual activity may be important so as not to induce a sense of shame or regret, i.e., denial. This is evidenced by studies indicating that if an adolescent engaged in a particular behavior, they were more likely to believe that they still met the definition of a virgin.[31] Among those 15–19 years old, those who remain a "technical virgin" are motivated more by the fear of pregnancy or STIs and less by religion and morality.[32]

The American Academy of Pediatrics has identified the sexual behaviors of American adolescents as a major public health problem.[33] The Academy is concerned about the prevalence of sexually transmitted diseases in sexually active teenagers and about the very high rate of teenage pregnancy in the United States compared to other developed countries.

Research into adolescents' sexual behavior in situations outside traditional dating situations, commonly referred to as hooking up, shows that adolescents underestimate the risk involved in such situations.[9][34] With all the issues and problems relating to adolescent sex, "ideally, they won’t be having sex."[35]

Teen pregnancies—defined as pregnancies in women under the age of 20, regardless of marital status—in the United States decreased 28% between 1990 and 2000, from 117 pregnancies per every 1,000 teens to 84 per 1,000.[3] The 2008 rate was a record low and represented a 42% decline from the peak rate of 117 per 1,000, which occurred in 1990.[19] From 2009 to 2010, the teen pregnancy rate dropped 9%, the biggest one year drop since the 1940s.[36]

Each year, almost 750,000 girls aged 15–19 become pregnant. Two-thirds of all teen pregnancies occur among the oldest teens (18–19-year-olds).[19] Of them, 82% are unplanned, accounting for about 20% of all unintended pregnancies annually.[19] Of pregnancies among 15–19-year-olds girls in 2008, 59% ended in birth, 26% in abortion, and the rest in miscarriage.[19] Overall, 68 pregnancies occurred per 1,000 girls aged 15–19 in 2008. Nearly 7% of 15–19-year-old girls become pregnant each year. Pregnancies are much less common among girls younger than 15. In 2008, 6.6 pregnancies occurred per 1,000 teens aged 14 or younger. In other words, fewer than 1% of teens younger than 15 become pregnant each year.[19] Stillborn and newborn deaths are 50% higher for teen moms than women aged 20–29, and are more likely to have a low birth weight.[37]

Teenage birth rates, as opposed to pregnancies, peaked in 1991, when there were 61.8 births per 1,000 teens, and the rate dropped in 17 of the 19 years that followed.[36] One in four American women who had sex during their teenage years will have a baby before they are married, compared to only one in ten who wait until they are older.[38] Even more will experience a pregnancy. Of women who have sex in their teens, nearly 30% will conceive a child before they are married. Conversely, only 15% of women who don't have sex in their teens will become pregnant before they are married.[38] Of all women, 16% will be teen mothers.[39]

According to a study, girls who participate in girls-only activities are far less likely to experience a teenage pregnancy and less likely to be sexually active in general.[40] Participating in competitive sports has also shown to have an effect for girls. A study published in 1999 found that female adolescents who participated in sports were less likely than their non-athletic peers to engage in sexual activity and/or report a pregnancy.[41] Males interested in arts are also less likely to be involved in a pregnancy situation. It is unclear whether these correlations are causal or the reflection of the underlying bias of the considered population. The study that reported these findings did not take into account the sexual orientation of the subjects.[41]

A survey by the National Campaign to Prevent Teen Pregnancy found that "7% of youth used alcohol the first time they had sex, and 6% used alcohol the most recent time they had sex."[42] In another study, teens aged 15–19 accounted for 15.5% of abortions in 2009, and patients aged 20–24 made up 32.7%. Together adolescents aged 15–24 made up just under half (48.2%) of the 784,000 abortions reported to the CDC that year.[43]

According to one study, laws that require parental notification or consent before a minor can obtain an abortion "raise the cost of risky sex for teenagers."[44] The study found that states which have enacted such laws have seen lower gonorrhea rates among teens than states that do not have such laws. The researchers of the study believe these laws lower the gonorrhea rate because teens reduce the amount of sexual activity they have and are more fastidious in their use of birth control.[44] On the contrary, statistics released from the World Health Organization (WHO) indicate that more restrictive laws on abortions do not necessarily mean fewer abortions; the abortion rate one year for Latin America (where, broadly speaking, abortions are generally made illegal) was 32 per 1000 people, whereas the abortion rate for Western Europe (where overall the laws are more relaxed) was 12 in 1000.[45]

Each year, between 8 and 10 million American teens contract a sexually transmitted infection (STI/STD),[note 1] almost half of the 19 million STIs reported for all age groups in the United States.[19][46]

Lloyd Kolbe, director of the Center for Disease Control's Adolescent and School Health program, called the STI problem "a serious epidemic."[47] The younger an adolescent is when they first have any type of sexual relations, including oral sex, the more likely they are to get an STI.[48][49]

HPV (Human papillomavirus) is the most common STI among teens (as well as adults).[50] In a CDC study, 18% of teen girls were infected with HPV.[51] Another study found that HPV infections account for about half of STIs detected among 15- to 24-year-olds each year.[19][52] While HPV infections may not cause any disease and is often asymptomatic, it can cause genital warts and even cancer.

After HPV, trichomoniasis and chlamydia are the most common STI diagnoses among 15- to 24-year-olds; combined, they account for slightly more than one third of diagnoses each year.[19]Genital herpes and gonorrhea together account for about 12% of diagnoses. HIV, syphilis and hepatitis B account for less than 1% of diagnoses,[19] however young people aged 13–24 accounted for about 21% of all new HIV diagnoses in the United States in 2011.[19]

Researchers from the CDC have noted that teenagers often do not understand the risks associated with sexual activity. "Research suggests that adolescents perceive fewer health-related risks for oral sex compared with vaginal intercourse. However, young people, particularly those who have oral sex before their first vaginal intercourse, may still be placing themselves at risk of STIs or HIV before they are ever at risk of pregnancy."[49] "Several studies have documented that oral sex can transmit certain STIs, including chlamydia, genital herpes, gonorrhea and syphilis. Teenagers and young adults engaging in sexual activity are at increased risk of STIs or HIV."[49]

A 2008 study by the CDC found that one in four teen girls, or an estimated 3 million girls, has an STI.[51] The study of 838 girls who participated in a 2003–04 government health survey found the highest overall prevalence among black girls; nearly half in the study were infected. This is compared with 20% among both whites and Mexican-American teens.[53] The same study found that, among those who were infected, 15% had more than one STI, and 20% of those who said they had only one sexual partner were infected.[51]

In a 2011 study by the CDC, 7.1% of females and 2.1% of males aged 15–24 were infected with chlamydia,[54]:65 historically the most prevalent of all STIs in the general population (after HPV).

Benefits to teen sex do exist, by extension of data on the benefits of sex: It can relieve pain, burn calories, relieve stress, help the immune system, stimulate the mind and mellow one's mood. Other health benefits have been observed in older men—decreased risk of stroke and heart attack—but the same benefits have not been confirmed in teenage patients.[55]

The earlier onset of puberty can produce sexual drives at a time when teens are not yet fully socialized to understand the potential social and emotional consequences of sexual activities.[56][57][58][59][60] Some scholars claim that the risk for depression is "clearly elevated" for the sexually active of either gender.[61]

"We tend to focus on the health consequences of having sex, like pregnancy and STIs, but we also need to talk to [teens] about all the emotional consequences," some experts say.[15]

Some research suggests that two-thirds of sexually active girls wish they had waited longer before having sex.[62] Of seniors in high school, 74% of girls regret sexual experiences they have had.[63]

For girls, even modest involvement in sexual experimentation elevates depression risk.[64] Sexually active teenage girls are more than twice as likely to suffer depression compared to those who are not sexually active.[65]

Sex therapists have found that the roots of sexual issues facing adults often date back to regretful teenage experiences.[15] Research has also found that being abstinent in the teen years was associated with better mental health at age 29.[66] Girls who were virgins at age 18 were also less likely to have a mental illness at age 40.[67]

Girls are "at particular risk for experiencing negative social and emotional consequences of having any type of sex," including oral sex.[14] Girls are more than twice as likely as boys to say they felt bad about themselves and more than three times as likely to say they felt used as a result of engaging in sex[15] or hookups.[15][68]

In a study of casual sex among adolescents, many girls believed they could have a purely sexual experience with no emotional ties, and they believed it was sexist to assume otherwise. However, the study found that both the girls and the boys who were hooking up often were depressed and didn't feel very good about themselves.[69]

When engaging in sexual acts the body produces oxytocin, a chemical produced in the brain to promote feelings of connection and love. Production of oxytocin increases during the adolescent years. It has a larger effect on girls, suggesting it may make them care more about relationships and feel connections with others more intensely than boys.[55][70]

Teen dating violence is defined as the physical, sexual, psychological or emotional violence within a dating relationship, as well as stalking.[71] This includes electronic forms (e.g., threatening text messages, excessive yelling or cursing at someone in a phone message) as well as face-to-face forms.[71]

Girls who have engaged in sexual intercourse are five times more likely than their virgin peers to be the victim of dating violence.[72] Girls who were intentionally hurt by a date in the past 12 months are at a "significantly elevated risk for a broad range of sexual health concerns and for pregnancy."[72] Girls who have been victims are also twice as likely to report high levels of multiple sexual partners.[72]

Sexual assault is any involuntary sexual act in which a person is threatened, coerced, or forced to engage against their will, or any sexual touching of a person who has not consented. This includes but is not limited to rape, groping, forced kissing, or the torture of the victim in a sexual manner.[73][74] In legal terms, sexual assault is a statutory offense in the United States, varying widely state-to-state.

Outside of law, the term rape has a less distinguished meaning and is often used interchangeably with sexual assault.[75][76]

Most rape victims are in their teens or young twenties: according to a study by the CDC and Department of Justice, 83% of rape victims interviewed were under the age of 25, and 54% were under the age of 18. 1 in 6 women had been raped in the study, and 1 in 33 men.[77] 1 in 5 women and 1 in 7 men who have experienced sexual violence first experienced this through dating violence as a teen.[78]

Sexting, the sending of sexually explicit messages and/or photographs, has become increasingly popular with adolescents. However, sexting can "glamorize and normalize sex in a way that might cause some teenagers to start having sex earlier, or in unhealthy ways."[82]

More than one fifth of teens have sent sexually suggestive text messages or nude photographs of themselves online.[83] Teens who photograph or film themselves or receive photos of others, known as sexting, can be charged with child pornography.[84] Others who post the photos online could also be charged with child pornography and face prison time.[85] Sexting can be considered sexual harassment.[82]

Sexting is linked to psychological distress among teens. Those involved in sexting are more likely to report a suicide attempt, and have twice the odds of reporting depressive symptoms as students who aren't involved in sexting. "For girls who send the sexts ... there is a disillusionment and a sense of betrayal when it's posted everywhere. When it gets forwarded to multiple boys at multiple schools and also other girls ... a girl starts getting called names and her reputation is ruined."[86]

Boys who are victims of sexually predatory teenage girls can also be devastated. Sexually predatory girls will ask a boy, particularly a sexually naive boy, for photos, and "he's sort of flattered and he feels like a big guy and then she sends them around."[86] Unbeknownst to them at the time, their compliance can cause lasting harm.

Often girls who take racy photos of themselves "want to be admired, want someone to want them. A lot of them are lonely and starved for attention. A lot of girls believe they have no choice but to pose in this way. There are also the thrill seekers who do it because it's "edgy and cool."[85]

Experts say that sexting poses a serious problem, partly because teens do not understand that the images are permanent and can be spread quickly. "It does not click that what they’re doing is destructive, let alone illegal."[87] "Once they are out there, it spreads like a virus," police say.[88]

Each state has its own age of consent. Currently, state laws designate the age of consent as 16, 17, or 18, with more than half of the states designating 16 as the age limit. However, the five most populous states all have a higher age of consent (California: 18, Texas: 17, New York: 17, Florida: 18 and Illinois: 17).

In some common law jurisdictions, statutory rape is sexual activity in which one person is below the age required to legally consent to the behavior.[89] Although it usually refers to adults engaging in sex with minors under the age of consent,[89] it is a generic term, and very few jurisdictions use the actual term "statutory rape" in the language of statutes.[90]

In statutory rape, overt force or threat need not be present. The laws presume coercion, because a minor or mentally challenged adult is legally incapable of giving consent to the act. Statutory rape laws are based on the premise that until a person reaches a certain age, that individual is legally incapable of consenting to sexual intercourse. Thus, the law assumes, even if he or she willingly engages in sexual intercourse, the sex is not consensual.[19]

Often, teenage couples engage in sexual conduct as part of an intimate relationship. This may start to occur before either participant has reached the age of consent, or after one has but the other has not. In most jurisdictions, the person who has reached the age of consent would be guilty of the statutory rape provision. In some jurisdictions (such as California), if two minors have sex with each other, they are both guilty of engaging in unlawful sex with the other person.[91][92] Most jurisdictions consider the act itself to be prima facie evidence of guilt, as any consent between partners, even if freely given, does not meet the standard of law, as it is given by a person the law has defined as being incapable of giving consent. Thus the accused individual often has no defense.

These aspects have often been considered unjust, leading to the passage of so-called Romeo and Juliet laws, which serve to reduce or eliminate the penalty of the crime in cases where the couple's age difference is minor and the sexual contact is only considered rape because of the lack of legally recognized consent.

Research indicates that sexual messages contained in film, television, and music are becoming more explicit in dialog, lyrics, and behavior. In television programming aimed at teens, more than 90% of episodes had at least one sexual reference in it with an average of 7.9 references per hour.[96] Researchers have found a correlation between the amount of television with high sexual content that teenagers watch and an increased likelihood of them becoming pregnant or fathering a child out of wedlock, and believe that reducing the amount of sexual content adolescents watch on television could substantially reduce the teen pregnancy rate.[97] By contrast, other scholars have argued that such claims have been premature; Steinberg and Monahan found that media effects diminished once other factors were controlled.[95]

Scholarly studies suggest that approximately 15% of youth intentionally seek pornography in a given year.[98] Donna Freitas, author of The End of Sex: How Hookup Culture is Leaving a Generation Unhappy, Sexually Unfulfilled, and Confused About Intimacy, has this to say about porn:[32]

Many boys learn to assume that the things women do in porn—how they dress and act around men—is also how women are supposed to act in real life. These same boys are learning to expect girls their own age to act like the women in porn videos, too ... Social media and Internet porn are influencing junior-high and high-school girls' understanding of sexiness. Girls are learning to use porn and porn archetypes to impress boys as early as middle school.

Both boys and girls feel pressure from their friends to have sex. The perception adolescents have of their best friends' sexual behavior has a significant association with their own sex behavior.[99] Sexually active peers have a negative effect on adolescent sexual delay; however, responsive parent-adolescent sex discussions can buffer these effects.[100]

In a 2003 study, 89% of girls reported feeling pressured by boys to have sex, while 49% of boys reported feeling pressured by girls to have sex. In contrast, 67% of boys felt pressured by other boys, while 53% of girls felt pressured by other girls.[16]

Adolescents who reported sexual activity had high levels of reputation-based popularity, but not likeability among peers; however, sex with more partners was associated with lower levels of popularity.[99]

Two main forms of sex education are taught in American schools: comprehensive and abstinence-only. Comprehensive sex education covers abstinence as a positive choice, but also teaches about contraception use and the avoidance of STIs if the teen becomes sexually active. A 2002 study conducted by the Kaiser Family Foundation found that 58% of secondary school principals describe their sex education curriculum as comprehensive.[6] The difference between these two approaches, and their impact on teen behavior, remains a controversial subject in the United States.

There have been numerous studies on the effectiveness of both approaches, and conflicting data on American public opinion. Public opinion polls conducted over the years have found that the majority of Americans favor broader sex education programs over those that teach only abstinence, although abstinence educators recently published poll data with the totally opposite conclusion.[101][102][103] The poll sponsored by the National Abstinence Education Association and conducted by Zogby International found that:[104]

When parents become aware of what abstinence education vs. comprehensive sex education actually teaches, support for abstinence programs jumps from 40% to 60%, while support for comprehensive programs drops from 50% to 30%. This sharp increase in support of abstinence education is seen across all political and economic groups. The majority of parents reject the so-called "comprehensive" sex education approach, which focuses on promoting and demonstrating contraceptive use. Sixty-six percent of parents think that the importance of the "wait to have sex" message ends up being lost when programs demonstrate and encourage the use of contraception.

Experts also encourage sex educators to include oral sex and emotional concerns as part of their curriculum. Their findings also support earlier studies that conclude:[14]

...sexual risk-taking should be considered from a dynamic relationship perspective, rather than solely from a traditional disease-model perspective. Prevention programs rarely discuss adolescents’ social and emotional concerns regarding sex.... Discussion about potential negative consequences, such as experiencing guilt or feeling used by one's partner, may lead some adolescents to delay the onset of sexual behavior until they feel more sure of the strength of their relationship with a partner and more comfortable with the idea of becoming sexually active. Identification of common negative social and emotional consequences of having sex may also be useful in screening for adolescents at risk of experiencing more-serious adverse outcomes after having sex.

Proponents of this approach argue that sexual behavior after puberty is a given, and it is therefore crucial to provide information about the risks and how they can be minimized. They hold that abstinence-only sex ed and conservative moralizing will only alienate students and thus weaken the message.

A report issued by the Department of Health and Human Services has found the "most consistent and clear finding is that sex education does not cause adolescents to initiate sex when they would not otherwise have done so." The same report also found that:[21]

Family life or sex education in the public schools, which traditionally has consisted largely of providing factual information at the secondary school level, is the most general or pervasive approach to preventing pregnancy among adolescents.... Adolescents who begin having sexual intercourse need to understand the importance of using an effective contraceptive every time they have sex. This requires convincing sexually active teens who have never used contraception to do so. In addition, sexually active teens who sometimes use contraceptives need to use them more consistently (every time they have sex) and use them correctly.

Abstinence-only sex education tells teenagers that they should be sexually abstinent until marriage and does not provide information about contraception. In the Kaiser study, 34% of high-school principals said their school's main message was abstinence-only. Some Christian organizations advocate abstinence-only sex education because it is the only approach they find acceptable and in accordance with their churches' teachings.

Some organizations promote what they consider to be "sexual purity", which encompasses abstaining from not only intercourse before marriage, but also from sexual thoughts, sexual touching, pornography, and actions that are known to lead to sexual arousal. Advocates of abstinence-only sex education object to comprehensive curricula which fail to teach moral behavior; they maintain that curricula should promote conventional (or conservative) morality as healthy and constructive, and that value-free knowledge of the body may lead to immoral, unhealthy and harmful practices.

A comprehensive review of 115 program evaluations published in November 2007 by the National Campaign to Prevent Teen and Unplanned Pregnancy found that two-thirds of sex education programs focusing on both abstinence and contraception had a positive effect on teen sexual behavior. The same study found no strong evidence that programs that stress abstinence as the only acceptable behavior for unmarried teens delayed the initiation of sex, hastened the return to abstinence, or reduced the number of sexual partners.[109] According to the study author:

Even though there does not exist strong evidence that any particular abstinence program is effective at delaying sex or reducing sexual behavior, one should not conclude that all abstinence programs are ineffective. After all, programs are diverse, fewer than 10 rigorous studies of these programs have been carried out, and studies of two programs have provided modestly encouraging results. In sum, studies of abstinence programs have not produced sufficient evidence to justify their widespread dissemination.

Most teens (70%) say they have gotten some or a lot of information about sex and sexual relationships from their parents. Other sources of information include friends at 53%, school, also at 53%, TV and movies at 51% and magazines at 34%. School and magazines were sources of information for more girls than boys, and teens "who were sexually active were much more likely to say they got information about sex from their friends and partners."[110] Less than half of parents with daughters under 18 talk to their girls about how to say no to boys, and about half talk to them about contraception.[2]

Adolescents whose parents talked to them at a young age felt more comfortable as they grew and were more likely to make personal decisions about sexual behavior that reflects the parental values and morals.[111]

Studies have suggested that fathers generally tend to avoid sexual conversations with their children.[112] Many fathers have uncertainties on how to start to the conversation. Other times they simply put the initiative on their daughters to come to them with questions or issues.[113] Even when the conversation is launched fathers tend to be judgmental or only talk about abstinence. Fathers are more likely to forbid daughters from having sex when they are talking. Wilson et al. (2010) found that some fathers felt that talking about the potential consequences of sex was easier than talking about sex itself.[114] Fathers overall tend to apply more orders when talking to their daughters than giving them unbiased information or simply listening and trying to give them their best advice.

Hutchinson and Cederbaum (2011) studied father-daughter communication and found that increased father-daughter communication delayed sexual debut and decreased the frequency of engagement in sexual intercourse.[115] They also found that responsible sexual behavior among adolescent females was associated with positive father-daughter communication regarding men, dating, sex, and marriage. On the other hand, fathers who were absent had been linked to higher rates of sexual activity and teen pregnancy among female adolescents.[116] Fathers have a greater impact on daughters than they think, but fail to recognize it because they don’t believe they should be discussing sex with their daughters or simply leave it to the mothers.

Girls who participate in athletics, artistic, or academic extracurricular activities are less likely to be sexually active than girls who don't participate in any. Female athletes have "significantly fewer sex partners, engaged in less frequent intercourse ... and began having sex at a later age." For boys, those who participate in sports are slightly more likely to be sexually active, and those who are in artistic activities are considerably less likely.[117]

Religious adolescents lose their virginity three years later than the average American. On average, those with strong religious backgrounds become sexually active at age 21.[118]

Studies have shown stressed teens and teens without sufficient familial involvement tend to have more sex.[119][120]

According to a study based on a sampling of teenagers in Massachusetts, sexual minority youth—that is, those who identify as gay, lesbian, or bisexual or had any same-sex sexual contact in their lifetimes—were significantly more likely than other students to report lifetime sexual intercourse (72% vs. 44%).[121] The same study found that sexual minority youth were more likely to report sexual intercourse before age 13 (18% vs. 4%), sexual intercourse with four or more partners in their lifetimes (32% vs. 11%), and recent sexual intercourse (55% vs. 33%).

Among students in the Massachusetts study who ever had sexual intercourse in their lifetimes, sexual minority youth were significantly more likely than other students to report "having been or gotten someone pregnant (15% vs. 4%) and having been diagnosed with HIV or another STI (10% vs. 5%)."[121][122] Several studies have found that gay youths are represented disproportionately among adolescents who drop out of school, run away from home, abuse alcohol and other drugs, engage in prostitution, or attempt, contemplate and successfully commit suicide.[123]

^Although STD has been the term used the longest (for sexually transmitted disease), the preferred term now is STI, for sexually transmitted infection, reflecting the fact that it is possible to become infected but not display any symptoms